1. Field of the Invention
The present invention relates to a recording medium suitable for use in recording with inks and a production process thereof. In particular, the present invention relates to a recording medium for ink-jet printing, which can provide images high having optical density and bright in color tone, and has excellent ink-absorbing capacity, a production process thereof, and an image forming process using such a recording medium.
2. Related Background Art
In recent years, an ink-jet recording system, in which minute droplets of an ink are ejected by any one of various working principles to apply them to a recording medium such as paper, thereby making a record of images, characters and/or the like, has been quickly spread as a recording apparatus for various images in various applications including information instruments because it has features that recording can be conducted at high speed and with low noise, color images can be formed with ease, recording patterns are very flexible, and development and fixing process are unnecessary. Further, it begins to be applied to a field of recording of full-color images because images formed by a multi-color ink-jet system are comparable in quality with multi-color prints by a plate making system and photoprints by a color photographic system, and such printed images can be obtained at lower cost than the usual multi-color prints and photoprints when the number of copies is small.
With the improvement in recordability such as speeded-up and high-definition recording, and full-coloring of images in the ink-jet recording system, recording apparatus and recording methods have been improved, and recording media have also been required to have higher properties. In order to satisfy such requirements, a wide variety of recording media have heretofore been proposed. For example, Japanese Patent Application Laid-Open No. 55-5830 discloses paper for ink-jet recording, in which a coating layer having good ink absorbency is provided on a surface of a substrate, and Japanese Patent Application Laid-Open No. 55-51583 discloses that amorphous silica is used as a pigment in a coating layer.
Besides, recording sheets having an ink-receiving layer using an alumina hydrate of a pseudo-boehmite structure have been proposed in U.S. Pat. Nos. 4,879,166 and 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 5-32413 and 5-32414.
Further, Japanese Patent Application Laid-Open No. 2-276670 discloses alumina sol which forms a needle-like alumina hydrate aggregate oriented in a certain direction when the alumina sol having a solids concentration of 7% by weight is diluted to 1/100 with purified water, and the diluted alumina sol is dropped on a hydrophilized collodion membrane and dried. Japanese Patent Application Laid-Open No. 7-76162 describes the fact that the b-axis of a boehmite crystal is preferably oriented perpendicularly to the plane of a sheet. Japanese Patent Application Laid-Open No. 9-30115 describes a recording medium having a specific pore structure and a degree of orientation of 0.5 or lower. Japanese Patent Application Laid-Open No. 8-132731 describes a recording medium having a degree of parallelization of 1.5 or higher. However, the conventional recording media have involved the following problems.
1. The conventional recording media using pseudo-boehmite have involved a problem that the resulting ink-receiving layer tends to cause haze. In order to cope with this problem, the ink-receiving layer is controlled to have to a specific pore structure as described in Japanese Patent Application Laid-Open No. 2-276670, or to orient a pore structure and boehmite crystals as described in Japanese Patent Application Laid-Open No. 9-30115. However, to lessen pores having a large radius in a recording medium may result in the impairment of ink absorbency, and the uniform orientation of the boehmite crystals has involved a problem that producing conditions are difficult to control.
2. Japanese Patent Application Laid-Open No. 7-76162 describes a recording medium in which a silica layer is laminated on a pseudo-boehmite layer. The idea described in the above document relates to the prevention of scratch marking by providing the silica layer. However, this method involves a problem that scratch marking is reduced, but blow marking cannot be prevented.